Bearings of this type are already known from the prior art and are used in a motor vehicle, for example, for mounting the engine. Usually, the outer part is formed, for example, in a cylindrical or sleeve-like manner and the elastomer body has at least one spring strut, preferably at least two spring struts, which connect the for example sleeve-like inner part to the outer part. The use of two spring struts on which the inner part is mounted in the direction of gravitational force has the advantage that as a result better transverse stiffness can be achieved than with just one spring strut, which would operate as a pressure buffer. Also, two spring struts subjected substantially to shearing force are advantageous in order to generate a linear force-line path.
The spring strut is or the spring struts are provided substantially below the inner part in the direction of the weight force and thus substantially in the radial direction of the inner part and outer part, that is, in the plane perpendicular to the direction of insertion (longitudinal axis) of the plug-in holder. However, other geometric designs of the bearing are likewise possible.
The inner part contains an insertion opening into which a plug-in holder can be inserted in the axial direction of the bearing (longitudinal axis). For example, the engine of a motor vehicle can be secured to the plug-in holder such that, in the case of a bearing installed in a motor vehicle, the weight force of the engine is perpendicular to the longitudinal axis of the bearing, the longitudinal axis extending in the axial direction of the outer part. The engine of the motor vehicle is then mounted resiliently in the radial direction by the spring struts of the elastomer body.
During the production of such bearings, a gap is generally necessary in molding terms, this gap being enlarged even further by the shrinkage of the elastomer material of the elastomer body during the cooling process. If, when the bearing is employed in the motor vehicle, the spring struts are compressed in the direction of gravitational force because of the weight force of the vehicle components mounted on the plug-in holder, then the air gap is further enlarged in the radial direction (that is, counter to the direction of gravitational force) above the inner part with respect to the outer part. However, this air gap reduces the service life of the elastomer body and influences the force-travel characteristic of the bearing.
It has been shown that the service life of the elastomer body and thus of the entire bearing can be considerably increased if the elastomer body is preloaded in the radial direction such that the supporting spring struts are subjected to compressive stress. This is because, as a result of the preload, the radial spring travel which the spring struts permit is limited at least in the direction of tension. For this purpose, the spring travel which the spring struts allow is limited by stops in the elastomer body.
This can take place by way of additional elastomer and/or thermoplastic and/or metal components which are introduced into the air gap in order as a result to configure the progression of the spring struts in the tension direction. Thus, a preload can be created by a stop which is arranged between the inner part and the outer part of the bearing such that the elastomer body of the bearing is preloaded. As a result of the introduction of the stop, preloading of the elastomer body can be reliably achieved. However, it should be noted that the introduction of the stop represents an additional working step which makes the production of the bearing more complicated and thus more expensive.
DE 10 2009 044 093 A1 discloses a bearing described initially herein, which has a stop buffer located on the outer part and the plug-in holder of which has a stop. If the plug-in holder is now pushed in the axial direction into the inner part, the stop thereof presses radially against the stop buffer of the outer part and thus establishes a preload. As a result, a production step is saved since the plug-in holder and the stop are introduced together.
A disadvantage here is that the plug-in holder and stop are produced in one piece from the same material, for example cast aluminum, in order as a result to save a further production step which would be necessary in order to produce these elements separately and then assemble them. Thus, with the arrangement in DE 10 2009 044 093 A1, a very hard preload is achieved since this is brought about by a metal plug-in holder and stop. A further disadvantage is that the overall travel of the spring struts in the tension direction (this overall travel being determined by the spacing of the metal components) is reduced, and the stiffness rises sharply.